There are numerous manufacturing operations calling for the welding of a multiplicity of parts together to form a complex assembly of exacting dimensional tolerances and physical integrity. One such assembly is a nuclear fuel bundle spacer of the construction disclosed in commonly assigned Matzner et al. U.S. Pat. No. 4,508,679. These spacers are comprised of a plurality of tubular cells or ferrules, each approximately 1.2 inches long and 0.64 inches in diameter, with a wall thickness of approximately 0.025 inches. The ferrules are arranged in a matrix array with contiguous peripheral points of adjacent ferrules conjoined by butt welds. The bore of each ferrule provides a passage for receipt of an elongated fuel rod of the bundle. The fuel rods are centered and laterally supported in the ferrule bores between resilient springs and opposed stops integrally formed near the upper and lower ferrule edges. If the laser beam is not precisely centered on the weld sites constituted by the points of virtual peripheral abutment between the upper and lower edges of the ferrule, an unacceptable butt weld is achieved due to insufficient weld penetration. Also, an off-center laser beam can impinge on the fuel rod centering springs located beneath the ferrule edges, inflicting damage thereon. In either case, the resulting spacer is unacceptable and must be scrapped.